The match function in pcre_exec.c in PCRE before 8.37 mishandles the /(?:((abcd))|(((?:(?:(?:(?:abc|(?:abcdef))))b)abcdefghi)abc)|((*ACCEPT)))/ pattern and related patterns involving (*ACCEPT), which allows remote attackers to obtain sensitive information from process memory or cause a denial of service (partially initialized memory and application crash) via a crafted regular expression, as demonstrated by a JavaScript RegExp object encountered by Konqueror, aka ZDI-CAN-2547.
git.php.net/?p=php-src.git%3Ba=commit%3Bh=c351b47ce85a3a147cfa801fa9f0149ab4160834
vcs.pcre.org/pcre/code/trunk/ChangeLog?view=markup
vcs.pcre.org/pcre/code/trunk/pcre_exec.c?r1=1502&r2=1510
www.openwall.com/lists/oss-security/2015/08/04/3
www.openwall.com/lists/oss-security/2015/11/29/1
www.securityfocus.com/bid/76157
bto.bluecoat.com/security-advisory/sa128
bugs.exim.org/show_bug.cgi?id=1537
bugzilla.redhat.com/show_bug.cgi?id=1187225